It is known to produce isolatable electrical contact devices having two conducting components located at some distance from each other, each one of which can be connected to a conducting element, it being possible to establish an electrical connection between these two conducting components via a blade in the form of a conducting strip which can be moved between a closed position of the circuit in which it is in contact with the two conducting components and an open position of the circuit in which it is separated from these components.
Generally, the blade is mounted so that it can pivot between its closed position and its open position.
Isolatable electrical contact devices are often used in difficult environments, which are difficult especially in terms of vibration, dust or corrosive atmosphere.
The aim of the invention is to provide an isolatable contact which is highly reliable, including in difficult environments.
To achieve these objectives, the invention relates to an electrical terminal block comprising, inside an insulating casing:
two conducting components (3, 4) located at some distance from each other, each of which can be connected to a conducting element, for example via a wire;
a blade (5) in the form of a conducting strip which can be moved between a closed position of the circuit in which it is in contact with the two conducting components and an open position of the circuit, in which it is separated from these components;
a rod (7) translationally connected to the blade (5) and which can be moved axially in the casing (2) between an xe2x80x9cinsertedxe2x80x9d position in the casing in which the blade (5) is in the closed position of the circuit and a xe2x80x9cwithdrawnxe2x80x9d position in which the blade (5) is in the open position of the circuit;
means for holding the rod in a stable manner in one or the other of the two withdrawn or inserted positions.
According to the invention, the terminal block is characterized in that:
the means holding the rod (7) in the withdrawn position comprise a spiral spring (11) inserted between the casing and the rod (7); and
the means holding the rod in the inserted position are associated with the rod (7) itself.
In some applications, several contacts are juxtaposed and must be actuated in a coupled manner. In such a case, the rods associated with the various contacts are parallel and their free ends are connected by a bar-shaped element on which a drive rod acts, which drive rod, parallel to the rods of the various blocks, is equipped with means for holding the contacts in the closed position.
According to a first possibility, the means holding a rod in the closed position of the electrical contact comprise a finger extending perpendicularly from the rod and engaged in a groove made in the casing for guiding the rod, oriented parallel to the rod and comprising, at its end located closest to the contact, a 90xc2x0 return.
To close the contact, it is appropriate to slide the rod in a direction in which it is inserted into the casing, then to make it rotate when the finger extending from the rod butts against the lower end of the groove. In order to ensure proper locking of the rod in the closed position of the contact, the return of the groove for guiding the finger itself comprises, at its end, a notch for locking the finger.
To open the contact, it is appropriate to release the finger from the locking notch in which it is engaged, then to make the rod pivot until the finger is located in the groove made parallel to the axis of the rod. The spring then returns the rod to the open position of the contact. To actuate the rod in rotation, it is possible to provide the end thereof with a slot allowing the blade of a screwdriver to be engaged.
According to a second possibility, the means holding a rod in the closed position of the electrical contact comprise a finger extending perpendicularly from the rod and engaged in an inclined groove made in the casing for guiding the rod and having a notch for locking the finger in the position in which the rod is most engaged in the casing.
Advantageously, the groove is continuous and the casing in which it is made comprises, on its periphery, several successive groove portions successively corresponding to the movement of the rod toward the closed position of the contact and toward the open position of the contact.
In this case, the translational movement of the rod is accompanied by a rotational movement thereof. Insofar as the groove extends continuously over the periphery of the bore of the casing in which it is made, it is possible to make the rod pass from a withdrawn position to an inserted position then from an inserted position to a withdrawn position while always rotating the rod in the same direction.
According to yet another possibility, the means holding a rod in the closed position of the electrical contact comprise a ring which, engaged around the rod and mounted so that it is free in rotation and blocked in translation in the insulating casing, has two sawtoothed edges, the various teeth being defined by an inclined portion followed by a portion parallel to the axis of the ring, all the inclined portions being inclined in the same direction, the ring having axial grooves opening out in its inner wall, made alternately with the recessed regions of the sawtoothed profile, while the rod has two radially protruding lugs which are offset axially by a value at least equal to the width of the ring, in order to be located on either side thereof, the two lugs being offset circumferentially by a value substantially equal to the length of a tooth, the lug located on the side of the free end of the rod serving, by pressing against the inclined faces of the teeth of the ring, to produce the rotational drive of the ring, in order successively to bring the other lug pressing in the recess of a tooth, with an axial position of the rod corresponding to the closure of the contact, and on the inside of a groove, with an axial position of the rod corresponding to the opening of the contact. Any pressure exerted on the rod causes the notched ring to pivot, and the rod to pass from the closed position of the contact to the open position of the contact and so on and so forth.
In the embodiments in which the rod pivots when passing from the closed position to the open position of the contact and vice versa, the blade is mounted so that it can rotate freely on the rod which is associated with it and which is guided in translation, with rotational locking, in the insulating casing.